Manufacture of pure sulphur



Aug. 7, 1928. 1,680,079

W. H. BENTLEY MANUFACTURE OF PURE SULPHUR Filed Aug. 16, 1926 LID ND A) v21 m /%M Patented Aug. 7, 1923i turns STATES PATENT DFFICE.

'vvmmau HENRY BENTLEY, F BURNLEY, ENGLAND, AB BIGNOB OF TWU-THIBDS EU ddhlhl RILEY & SONS LIMITED, 0F HAP'I'ON', ENGLAND, A BRITISH comm,

EAN'UFAGTUEE OF PURE swarm hppllcatlou filed August is, 1926, Serial No. 128,561, and in Great Britain August i7, i925.

' My invention relates to an improved process tor the manufacture of pure sulphur, especially trom the crude sulphur of commerce.

a The main object ot the invention is to provide a cyclic process. Further objects are to 1provide improved methods of regenerating su phur trcm polysulphide solutions, and to provide improved methods of economically re vvorhing up crude sulphur into valuable products.

According to the present invention in its prelerred term crude sulphur is dissolved in the mother liquor lrom a previous operation it to form a solution ot soluble polysulphide vvhich is then treated with hydrogen sulphide under such conditions of temperature and pressure that elemental sulphur is precipitated. llt't'ter solution oi the crude sulnu phur the polysulphide solution is separated trom insoluble impurities e; g. by filtration. alkali or allraline earth polysulphide may be employed e. g. sodium or calcium polysulphide.

'llhe polysulphide is decomposed by hydrop en sulphide at a lovv temperature or under high pressure or both and the mother liquor is regenerated by the solution of crude sulphur therein at a high temperature or under reduced pressure or both. The hydrogen sulphide liberated in the process ct regeneration may be collected and used to decompppse the polysulphide to produce pure sulur. a

P The pure sulphur is separated by filtration and-Washed with Water until it is tree from adhering soluble salts and dried. I

The invention also includes an arrangement of apparatus suitable tor carrying out the process,

The invention Will be understood more clearly from the tollovving description and its scope will be defined in the appended claims.

M Tu a preferred term of the invention it may carry out the process in the a paratus illustrated in the accompanying rawing.

The jacketed pan 1 is charged through the hole 2 With Water, sodium sulphide and crude sulphur in quantities necessary to produce the desired strength of sodium polysulphide (preferably the Na h and the'mixture is agitated and at the same time heated by assing steam into the jacket 3 until the sulp ur goes into solelllll hil lid

htl

lllll -filter press lid by opening the tap 2t on the pentasulphide tion. The contents ot the pan 1 are then cooled to about fl0 C. by stopping the steam and circulating cold water through the gasket 3. The tap 4 on the outlet pipe 5 is then opened and the solution of the sodium polysulphide is run into a containing vessel 6 inside which it is passed through a simple filter bed 7. The space beneath the filterbed is 'suliicient to hold the whole olf one filtered charge. The container 6 is provided with vent pipes 8 and 9 carrying taps l0 and 11 respectively.

When the pan 1 is empty another batch of sodium polysulphide similar to the first is prepared in it, and While this is proceeding the contents of the container 6 are run into the jacketed pain it by opening the tap 13 on the outlet pi e la and the tap 15' on the vent pipe it. The sodium polysulphide now; in pan 1% is cooled to about ill" t1. by agitation and by circulating cold Water through the jacket 17,, The tape 13 and it are new closed and the taps l8 and id opened and the pump started vvhereby sulphuretted hydrogen is draw-n trorn the gas holder (not shovrn) along the ipe hi and thread alon the pipe at into t e pan 12 Where it is a scrbed by the sodium polysulphide which is hept in motion by an agitators The pan la is constructed to stand at least a pressure oil about t0 lbs. per square inch.

The introduction of the sulphuretted hy drogen causes the precipitation ct sulphur from the olysulphide and rvhile this is pre receding t e second charge ct sodium pol m sulphi .e in pan l is run into 6 three h t e filter to Then the next charge at cru e nullphur is introduced through the charge hole a and the lid cl 2 is securely bolted on, The pan l is put into communication with the pipe and the pair are tilled with sulphuretted hydrogen by first pumping out the air by starting the suction pump at and opening the tap it? on the pipe and then alter closan ing' the tap 2i opening the ta at on the pipe and thus admitting sulp uretted hydrogen -tram the gas holder.

The apparatus is now ready tor the filtra tion of the preci itated sulphur and When we the pressure at t, e as in the pan it has reached the amount ound by practice to be the most suitable the tap 31 on the outlet pipe 35.; is opened and the charge blown out oi the pan 12 through the filter press dill the no filtered liquor and excess gas passin along the pipes 33 and 25 into the pan 1. ere the excess gas disengages itself and passes along the pipe 30 back to the gasholder.

When the charge in the pan 12 has been blown out by the pressure of the sulphuretted hydrogen, the pump 20 is stopped and the taps 31, 18, and 19 are closed and the tap 34 on the branch pipe 35 is opened to allow the gas under ressure in the pan 12 to return to the gas older via the pipe 21. The second charge of sodium polysulphide standing in the container 6 is now run down into the pan 12 to await its treatment with sulphuretted hydrogen gas as just described and the tap 34cm the branch pipe 35 is closed. The purified sulphur in the filter press 23 is now washed with clean water and the first washings containing the bulk of the mother liquor adhering to the sulphur'is allowed to pass along the pipes 33 and 25 to the pan 1 and then the tap 24 is closed and the tap 36 on the pipe 37 is opened and the final wash water is allowed to run to the drain until a test shows that the last traces of mother liquor have been washed free from the sulphur. The sulphur is then blown as dry as possible by the stream of air, removed from the filter press and the dr ing completed in any suitable manner. he water and air pipes to the filter press are not shown in the sketch. The mother liquor and washings now in the pan 1 are agitated with the crude sulphur previously placed in the pa and the pan is heated by the steam jac et. Sulphuretted hydrogen is evolved and the sulphur goes into solution forminxgfii fresh batch of sodium polysulphide. en the sulphuretted hydrogen has all been evolved from the hot li uid the tap 29 is closed and the lid of the c arging hole 2 is taken off and the liquor is allowed to evaporate until the desired strength of polysul hide is attained and then the liquor is coo ed to 40 C. b circulating cold water throu h the jacket. The polysulphide solution is t en run into the container 6, being filtered through the bed 7, and remains there until the pan 12 is emptied and ready to receive it. Another charge of crude sulphur is introduced into the pan 1 and the charging hole 2 closed and the cycle of operations as just described is re eated continuously.

y making the filter press 23 suflicientl large several batches can be filtered before the necessity of washing and empt ing the press arises whereby some of the losses of sodium sul hide in the wash water can be avoided. T e slight losses of sodium sulphide are made good by the addition of the necessary quantities to the pan 1 when the crude sulphur is introduced.

In place of sodium sulphide I may employ other soluble sulphides such as postassim or calcium sulphides I have described the invention in such a way that it can be performed without the aid of any theory but we believe that a reversible reaction occurs by which polysulphide plus sulphuretted hydrogen give hydrosulphide plus sulphur and vice versa and in the preferred form of my process we cause the reaction to take place cyclically by operating alternatel in hot and cold solu tions. But I may also shift the equilibrium in the desired sense by the application of pressure .or vacuum in hot or preferably in cold solutions especially if in the latter case the crude sulphur is ground so finely that it dissolves with sufiicient speed.

I declare that what I claim is 1. The c clic process of sulphur w iich comprises ecomposing a polysulphide solution by hydrogen sulphide, separating the precipitated pure sulphur from the mother liquor and dissolving crude sulphur in the hydrosulphide mother liquor to give a polysulphide solution which can again be treated with hydrogen sulphide. 2. The cyclic process of pre aring pure sulphur which comprises disso ving crude sulphur in a hydrosulphide solution, removing solid impurities, treating the solution with hydrogen sulphide, separating the precipitated pure sulphur from the mother liquor and again dissolving crude sulphur in the mother 11 nor.

3. The eye ic process of pre aring pure sulphur which comprises disso ving crude sulphur in a hydrosulphide solution to evolve hydrogen sulphide, and then treating the solution with said hydrogen sulphide to precipitate pure sul hur therefrom.

4. The process 0 treating crude sulphur which comprises dissolving it in a hydrosulphide solution and removing solid impurities so as to give a purified polysulphide solution and hydrogen sulphide.

5.-The process of refining crude sulphur which consists in dissolvin it in a hydrosulphide solution and shiftin the equilibrium between hydrogen sulphide and solution so as to obtain solid pure sul hur.

6. The process of refining crud; sulphur which consists in dimolvingit in a hot hydrosulphide solution, filterin and cooling the liquor so obtained, an treating the cooled liquor with hydrogen sulphide and y separating the thus precipitated pure sulphur.

7. The step in the process of refiningcrude sulphur which consists in dissolving it in a hot h drosulphide solution. v

8. he step in the rocess of refining crude sulphur which consists in dissolvin it in a hot hydrosulphide solution and tering the ligplor so obtained.

9. e step in the process of refining crude sul hur which consists in dissolvi' g it in a hot ydroeulphide solution and filterreparing pure.

lift

hug" the liquor so ohtolned oud thou preehpl sulphuu flh'ouo the solution whieh is thou toting um sulphut' therefrom ready lot :turther use in the cycle,

10. he cyclic process of Prepuriug puma ll. The utep in the manufacture of pure sulphur Which eomprises dhosolviug erudle uulphulu which conslutu in preparing; u poly t sulphur in a hyduosulphidle solution at sulphide solution from crude sulphur aml lll raised; temperature, collecting the hydrogeu greoipitutlu said polyuulphide solution with sulphide evolved removing sollul lmpuritleo yduogeh uu phideu from the solution treating the cooled solo In Wttuuuu wheueol, l hove hereunto tion with the hyuh-ogeu sulphide ohfi sopo uiguedl home this hit dao1l Jul 1926..

Mt rating and recovering the preelpltuted put-e Wltlhlfi llllllR BlElLEYG 

